Dean Oliver is a genius

If you watched the Thunder/Bulls game the other night, especially somewhere in the second half, you might have had the same reaction that I and many other commenters here at DT had: how in the heck can we have a lead when we can’t get a rebound?”

Royce noticed it and made note in the recap, others suggested similar sentiments in the comments. I didn’t so much put the two together but just felt like we were getting crushed on the boards and hoped we didn’t give our lead away. The basketball gods smiled on us and we were able to put Chicago away despite a 25-13 deficit in offensive rebounds.

Offensive rebounds are flashy. They are like a 3-point shot in that they make you cheer in close games when your team gets one or makes one. If you are on the other side of the equation they feel like a gut punch. Your team is busy playing tough defense and they force the opponent into a tough shot that they miss only to see their freaking point guard come up with the Oreb and reset the offense with a fresh 24. It’s painful to watch and it makes you scream at your Center and Power Forward “why didn’t you box out“? Invariably after a few of those games or sequences us fans on the board begin to work out trade scenarios whereby we can ship off our inept bigs for guys that actually do box out and get the boards.

Rebounds are important. No doubt about it and I don’t want to diminish them. And the more we get the more we increase our chances of winning, but just HOW important are they?

A good maxim in life is that if you don’t know something, look it up. Consult an expert. Dean Oliver is a basketball savant. He is the author of Basketball on Paper, probably the most important book ever written on basketball statistical analysis. He’s the creator of the Offensive and Defensive Ratings that are used everywhere and also the “four factors”. In Basketball on Paper he has a little section in Chapter 6 titled “Does rebounding win games?”. I thought in light of the rebounding discussion since the Chicago game has been especially hot I would hit the highlights from Dean’s analysis.

Below is a copy of analysis Dean conducted where he took the games from 1998-2002 and began to see what the ultimate win percentage was for a given team when it won a given stat category. For example, the team that won the field goal shooting percentage against it’s competitor won 4,595 games, lost 1,132 games, (33 times they were tied in FG%) so that the team that won FG% won the game 78.7 % of the time (just read across).

Category

Won

Loss

Tied

Win %

Field Goal %

4595

1132

33

.801

Assists

4007

1414

339

.725

Def. Rbds.

3984

1485

291

.717

Ass./Turn ratio

3991

1717

52

.697

Total Rbds.

3526

1959

275

.636

FT's made

3453

2022

284

.624

Blocks

3182

1930

648

.609

Free Throw att.

3358

2174

228

.603

Fewer fouls

3256

2094

410

.601

Steals

3148

2037

575

.596

Fewer Turns

3114

2186

460

.581

Free throw %

3224

2459

77

.566

Offensive rbd. %

3205

2513

42

.560

Offensive rbds.

2452

2900

408

.461

Take a minute and digest what the data is saying. It’s telling us that offensive rebounds (and offensive rebounding rate-the percent of available offensive rebounds the team collected) had the weakest relationship with wins.

You might also notice that defensive rebounds are up near the top of the list. How do defensive rebounds correlate more closely with wins than do offensive rebounds? Dean explains that the relationship between defensive rebounds and field goal percentage blurs the value of the defensive rebound.

Oliver goes on to go micro with the data and look at how important each statistic correlates with wins when two teams are roughly even on field goal shooting percentages. I will save myself from creating another table and just tell you that offensive rebounding moves up the list to somewhere close to middle. Interestingly, when two teams meet that shoot evenly free throws made and fewer turns rise to the top of the list. Blocks and defensive rebounds drop to the bottom.

You could hypothesize and rabbit trail with the data a thousand ways to Sunday if you were so inclined but I will just repeat what Oliver wrote to close: “So, is rebounding important to winning games? Of course it is. Is it as valuable as shooting, getting to the line or controlling the ball (turns)? In the NBA it doesn’t appear to be so, though as mentioned above offensive rebounds do help to improve shooting percentages…”

We, as a middling at best offensive team could use all the Orebs we can get because they give us another whack at making a basket or getting to the line, but they aren’t the deal breaker to wins and losses.

@Jax Raging Bile DuctI think the reason you do a binary on the OREB Rate is because winning is a binary value as well. I think stats aren't legitimate if you use a continuous variable as the independent and a binary value as the dependent.

The best measure would probably look at the correlation between OREB Rate and point differential, then computing the r-squared of each variable to determine how much each variable contributes to winning. You could probably do a multiple regression analysis from there to get the interactions from the various factors and predict a point differential based on a set of inputs.

I would like that same kind of chart, only broken down by OREB%. I think a small advantage in OREB% is probably close to meaningless and it skews the statistics up there; when we're experiencing a 10%+ difference in OREB% I think the correlaiton to winning or losing should be stronger than what's represented up there. The vast majority of samples in Dean Oliver's data probably represent negligible advantages..

I think this all illustrates the 15 losses we have, or at least a lot of them, we shot worse and didnt make up for it with better offensive rebounding or less turnovers, most of our close games could have been one if we improved slightly on offesive rebounding margin or turnover margin

This is fun stuff. I don't think that it can be argued that differences in FGA between two teams is a major factor in winning. FGA within a game context are entirely connected to rebounding and turnovers. If you win those battles, it goes a long long way. Offensive rebounding and forcing turnovers, especially, seem to be almost the same in value to a team. Both give the ball back to your team, tend to lead to much higher percentage shots, and have momentum effects on the opposition. It's great that we (in general) get about the same offensive rebounds as the opposition, but that's only one half of the FGA issue (which I think is the more dominant connection to make). We are 7th from last in turnover rate. So, even if we grab an equal percentage (not number) of offensive rebounds, we are almost invariably handicapped by giving the ball away somewhere else. In fact, opponents average 1.5 more field goals than the Thunder every game.

Obviously, a great defense can take away that 1.5 shot advantage, but only if we have an adept offense to hurt an opponent when they don't shoot well. What I'm seeing, essentially, is that the Thunder tend to fail at the limiting factors of those things which they do well. They crash the offensive boards but can't get them on the defensive end, thus a wash in rebounding. They hold the opponent to a lower percentage than themselves, but they the opposition more possessions. They shoot slightly more free throws than the opposition, but actually foul a bit more as well. We are 4 games above .500, but a lot of our negative stats wash out our positive ones.

Ultimately, we can look at a lot of things that the Thunder do both well and poorly. Until we start winning on both sides of coins (high offensive AND defensive rebounds, low opponent FG% AND low team turnovers) we will be just good enough to win with better talent, but just bad enough to lose to inferior talent

I would like to see an average margin of offensive rebounding difference and how that affects the win/loss %. I would imagine that there is a special number of offensive boards, a median score maybe, where if your offensive rebound advantage was, say a net +5, you win, but less than that and you lose.

Oliver's chart treats the category like a binary value, and I don't think it is.

@J.G.Look at Oliver's stats. The second weskest correlation to wins is offensive rebounding%. So if we're giving up a high percentage of offensive rebounds, it's still not that big a deal. Defensive rebounds are highly correlated to win rates only because, as a total stat, they are correlated to better defensive FG% (more opponent missed shots = more rebounds). Defensive rebounding RATE is not that well correlated with winning. So don't be too worried about the defensive rebounding rate (at least according to the data).

And whenever the Thunder get sluggish closing out on shooters, that's when they start to fall apart.

Although, if you are not closing out on the perimeter, you are more likely to be in position for the rebound if they miss. Could have something to do with the numbers as well since the Thunder consistently contest every shot.... which puts even more pressure on their interior players to get the boards.

Joe :@J.G.I’m not sure I understand your question J.G., but for references sake, we are seventh best at offensive rebound rate–at getting the most of our available offensive rebound opportunities as expressed by percentage at 28.2%.But we are 7th worst at defensive rebound rate (or, not letting the other team get the offensive rebound) at 71.9%.Some of it is style of play, some of it is personnel.

That's exactly what I was saying, Joe. To me the most telling stat is not the Thunder's ability to grab offensive rebounds, but their inability to stop the other team from grabbing offensive rebounds, which is another way of saying that they're AWFUL in defensive rebounding rates (just forgot of the wording of the stat).

Style of play and personnel for sure (shot selection I would definitely highlight under style of play as being "young"), but in crunch time and into the playoffs, that is the stat that hurts the most and Oliver's statistics back it up. That's, to me, what has to be addressed.

Joe :@J.G.I’m not sure I understand your question J.G., but for references sake, we are seventh best at offensive rebound rate–at getting the most of our available offensive rebound opportunities as expressed by percentage at 28.2%.But we are 7th worst at defensive rebound rate (or, not letting the other team get the offensive rebound) at 71.9%.Some of it is style of play, some of it is personnel.

Yeah, my guess is that it's because the Thunder's guards are aggressive on the offensive glass - especially Westbrook. Durant is also better than most SF at gathering up a put-back.

@J.G.I'm not sure I understand your question J.G., but for references sake, we are seventh best at offensive rebound rate--at getting the most of our available offensive rebound opportunities as expressed by percentage at 28.2%.

But we are 7th worst at defensive rebound rate (or, not letting the other team get the offensive rebound) at 71.9%.

This kind of proves the point though. The Suns lead the league in FGA, but they actually gave up an average of over 3 FGA more to the other team because they turned the ball over more and were a poor offensive rebounding team, maybe? The Lakers, meanwhile, had 2 FGA more than their opponents because they turned the ball over less and secured offensive rebounds. The Warriors also allowed more FGA.

Being a fast team will lead to having more FGA over the course of the season but the effect that it has on FGA in a given game doesn't seem like it'd be significant to me..

I think DJ might be one of those players that plays well vs scrubs and can't bring the same game vs regulars. His defense before being shipped out was horrible!! and unless he magically found his game (also says in the article he has a post game) I bet when he gets called up he plays about the same.

@justinI think you're right. I wasn't thinking it through properly when I originally made that point. Speed/pace shouldnt have an impact on net FGA's. That should just be dictated by TOs, ORebs, and (to a lesser extent) FTAs.

Obviously, a faster team will be more FGA's over the season, but the net per game between the two teams shouldn't be affected.

This makes no sense to me maybe I’m stupid. So what if D’antoni’s team takes a shot in 7 seconds and the other team takes one in 20 seconds, they still can’t get another shot attempt until they regain possession of the ball, correct?In a vaccuum, turnovers and everything else being equal, how fast you take a shot doesn’t seem to me like it’d affect your FGA relative to the other team in that particular game. It’s like, if you’re playing chess and you take 5 seconds to act and the other guy takes 5 minutes, you still get the same number of moves.

Well strictly speaking you are absolutely correct. If you use the chess analogy, one move at a time. I was thinking more in terms of the whole game concept since the game doesn't happen in a vacuum. The Suns for example would likely get an offensive rebound and immediately put another shot up, whereas the Bobcats would pull it out after the Oreb and work for a good shot. That, plus turns and all that multiply over a season.

For example, last year the top five teams in FGA's were the Suns, Lakers, Warriors, Pacers and Knicks; not coincidentally the 5 fastest teams were the Warriors, Knicks, Pacers, Suns and the Nuggets, followed by the Lakers.

Here's my issue, since the Thunder are giving up a horrific amount of offensive rebounds to the other team, isn't that a better indicator of their defensive rebounding ability than raw #'s in defensive rebounds alone?

And since defensive rebounds are the third biggest indicator of winning percentages, shouldn't that be a huge concern?

Isn't there a statistic that shows defensive rebounds snagged out of total potential defensive rebounds? Or in other words, defensive rebounds they've grabbed versus how many they've lost to the other team. Isn't that the best measuring stick?

Bryan :I wish the book’s author had thrown shot attempts in the mix. I would like to see how that might change the analysis.But nice piece, Joe.

Well Oliver used two sets of data. One was from a company called STATS, where the games from 92-94 were used. In that data raw FGA's came in at 45.5%, which is just up from last, just above 3fga's. Oliver took the idea and ran his own numbers, which are the ones I put in the table, from a more current time frame and changed some of the categories. FGA wasn't one of the ones he used. But his data and the old STAT data are very similar so it is fair to say that FGA's don't correlate strongly with wins.

This makes no sense to me maybe I'm stupid. So what if D'antoni's team takes a shot in 7 seconds and the other team takes one in 20 seconds, they still can't get another shot attempt until they regain possession of the ball, correct?

In a vaccuum, turnovers and everything else being equal, how fast you take a shot doesn't seem to me like it'd affect your FGA relative to the other team in that particular game. It's like, if you're playing chess and you take 5 seconds to act and the other guy takes 5 minutes, you still get the same number of moves.

justin :@Mark!Being a volume scoring team doesn’t give you more attempts than the other team in a given game.. possessions are still relatively equal.

Well yes and no, it depends.By being a "volume scoring team" you mean fast, it can. If, like under D'Antoni, he preached getting a shot off in 7 seconds or less and the other teams usually use more of the shot clock, the faster team would get more shots. A faster team doesn't get more possessions, but it CAN theoretically get more shots.

I doubt FGA’s have a very strong correlation to wins, but instead of looking at an offensive rebound as leading to an additional attempt, you could arguably look at it as -removing- a FGA from the FG% calc, thus increasing the efficiency of the other team.

Agreed. And if the offensive rebounds come in the same possession, as when we allow three or four shots on the same possession, the effect is skewed because several rebounds only hurt you once. Obviously, that's not ideal if you need the ball back at the end of the game though.

Small difference in offensive rebounding % are probably useless.. I'd be interested in knowing the average difference in offensive rebounding % in the games Dean Oliver used for that data and how, say, a 10%+ difference in offensive rebounding % affects wins and losses. I'd imagine the effect is much stronger than what's shown here..

Also just another note, when you use % the differences can be so minute. Look at the 'ties' for FG%, OREB%, or A:TO ratio, there are much fewer. Some of the wins and losses for those statistics are probably very small values and effectively a 'tie'.

Heh, dunno why it escaped me that the table is looking at net. Still, I doubt there would be a strong correlation to wins if your team won on attempts. I think all the teams that have been built around volume scoring (last Golden State this year) would muddy up the waters in the win/loss column.

@Mark!15 more FGA is potentially 45 more points, even if its only them making 33% and 2 pointers thats still 10 more points then they would have scored, FGAs do matter, we would have blown out chicago if it were not for their offensive rebs

I doubt FGA's have a very strong correlation to wins, but instead of looking at an offensive rebound as leading to an additional attempt, you could arguably look at it as -removing- a FGA from the FG% calc, thus increasing the efficiency of the other team.

I would think there is definitely a lot of correlation between several of these stats (FTs made/FTs att, etc), but I would also assume the author knew what he was doing and took this into account when explaining what was most useful.

While offensive rebounding % is not as big a factor for winning games as shooting %, if you're giving up 15+ offensive rebounds in a game I think it's a bit more crippling than that table would indicate. Our last two opponents have had 99 FGA in regulation, 15+ more shot attempts.

Trackbacks

[…] It was a little ironic that after getting a major stop with 30 seconds left and still down one, OKC didn’t secure the rebound. Essentially, an offensive rebound for the Hornets turned out to be maybe the biggest play of the game because Chris Paul scored later on the extra possession to push the lead to three. But OKC did a fantastic job on the glass tonight, only allowing five offensive boards to the Hornets and outrebounded NOLA by nine for the game. For shame the Thunder couldn’t just grab one more. […]

[…] The Horseshoe: After an OKC win over the Bulls in which the Thunder were killed on the glass, Joe discovers that offensive rebounding may not be as critical to a team’s success as he previously thought. [Daily Thunder] […]